NEW YORK (Reuters Health) - Older adults' eyesight may suffer irreversibly if they don't have vision insurance, suggests a new study that argues eye health should be a mandatory part of regular health insurance policies.

Researchers found that people between 40 and 65 years old with vision insurance were twice as likely to see an eye doctor in the past year, compared to those without coverage.

And people who saw an eye doctor were more likely to be able to read printed material and to recognize someone from across the street.

"The study finds that having vision insurance increases the likelihood of an eye care visit, and that a prior-year eye care visit is associated with better vision status," the researchers write in the Archives of Ophthalmology.

Led by Yi-Jhen Li at the University of South Carolina in Columbia, the team notes that by 2020 it's estimated that over 5.6 million Americans will have an age-related eye disease that may lead to vision loss.

But the researchers add that permanent vision loss from some of those eye diseases - including glaucoma and cataracts - can be staved off with early detection and treatment.

"We want to get them in the door. If they get in the door, they're likely get what they need," said John Crews, a health scientist at the U.S. Centers for Disease Control and Prevention in Atlanta, who was not involved in the research.

"The problem from a public health point of view is, âwhat is impeding people from getting access to care?'" Crews said.

For the new study, Li and colleagues wanted to see if lack of vision insurance might stand in the way of working-age adults' ability to go to an eye doctor and whether that would affect their vision.

They used a 2008 survey of 27,152 people from across eight U.S. states. Of those, 11,541, or 43 percent, did not have vision insurance.

Of the 15,611 people who did have vision insurance, about 64 percent had seen an eye doctor in the previous year, compared to about 45 percent of people without coverage.

After taking certain traits - such as age, sex and race - into account, the researchers also found that generally healthy people with vision insurance were 24 percent more likely to report that they had no trouble recognizing friends from across the street and 34 percent more likely to say they could read printed material without problems, compared to those without the insurance.

The difference was even greater among a subsample of people who had common eye ailments like glaucoma, cataracts or age-related macular degeneration - those with vision insurance were 37 percent more likely to say they could read and 45 percent were more likely to recognize a friend from afar.

In both the general population and those with eye diseases, people who saw a doctor within the past year were also more likely to report better vision.

Li and colleagues, who were not available for comment, note in their paper that the age group they focused on, between 40 and 64, are too young to be covered by Medicare but are "at high risk for eye diseases that cause gradual vision loss that is preventable."

Theirs is the first study, they add, to examine how having vision insurance, versus general health insurance, influences how often people in this working-age segment of the population get regular eye care.

While 85 percent of the people in their sample had health insurance, the researchers write, just about 68 percent of those with health insurance had vision coverage. And, they say, their study indicates that it is vision insurance, but not health insurance, that determines not only whether people go to the eye doctor, but also the quality of their reported vision.

Making vision coverage a mandatory part of standard insurance policies would raise costs by about three percent, they conclude, calling that a "good value" compared to the costs of the vision loss that could be prevented.

The American Academy of Ophthalmology says older adults should have regular eye checkups every two to four years. The group recommends that people 65 years old and up see an eye doctor every one or two years.

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